/* ECO5207 Macro — exam-booklet paper, navy ink, blue-book blue,
   and one yellow highlighter reserved for "you are here" and matches. */
:root {
  --paper: #f3f6f9;
  --surface: #ffffff;
  --ink: #14213d;
  --ink-2: #3a4a66;
  --muted: #647189;
  --rule: #dce3ec;
  --rule-strong: #c5cfdc;
  --grid: rgba(43, 89, 195, 0.075);
  --accent: #2b59c3;
  --accent-ink: #1e3f8f;
  --accent-soft: rgba(43, 89, 195, 0.09);
  --hl: rgba(255, 216, 64, 0.72);
  --hl-strong: #ffd840;
  --up: #1b7f4e;
  --up-soft: rgba(27, 127, 78, 0.10);
  --down: #c4372b;
  --down-soft: rgba(196, 55, 43, 0.09);
  --warn: #a15c00;
  --code: #eaeff5;
  --card-rule: rgba(43, 89, 195, 0.12);
  --card-margin: rgba(214, 72, 60, 0.55);
  --shadow: 0 1px 0 rgba(20, 33, 61, 0.04), 0 8px 24px -12px rgba(20, 33, 61, 0.18);
  --radius: 12px;
  --sidebar: 276px;
  --top: 60px;

  --f-display: "Bricolage Grotesque", "Avenir Next Condensed", "Arial Narrow", system-ui, sans-serif;
  --f-body: "Atkinson Hyperlegible Next", "Atkinson Hyperlegible", -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  --f-mono: "Spline Sans Mono", ui-monospace, "SF Mono", Menlo, monospace;
  font-synthesis: none;
  color-scheme: light;
}
:root[data-theme="dark"] {
  --paper: #0e1524;
  --surface: #151f33;
  --ink: #e7edf7;
  --ink-2: #b9c4d8;
  --muted: #8793ab;
  --rule: #26334d;
  --rule-strong: #34446a;
  --grid: rgba(134, 168, 245, 0.075);
  --accent: #86a8f5;
  --accent-ink: #b3c8fa;
  --accent-soft: rgba(134, 168, 245, 0.13);
  --hl: rgba(255, 214, 70, 0.30);
  --hl-strong: #ffd646;
  --up: #5ad19a;
  --up-soft: rgba(90, 209, 154, 0.12);
  --down: #ff8a7a;
  --down-soft: rgba(255, 138, 122, 0.12);
  --warn: #f2b84b;
  --code: #1c2840;
  --card-rule: rgba(134, 168, 245, 0.10);
  --card-margin: rgba(255, 138, 122, 0.45);
  --shadow: 0 10px 30px -14px rgba(0, 0, 0, 0.6);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html, body { margin: 0; }
html { -webkit-text-size-adjust: 100%; }
body {
  background: var(--paper);
  color: var(--ink);
  font: 17px/1.65 var(--f-body);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-underline-offset: 3px; text-decoration-thickness: 1px; }
a:hover { color: var(--accent-ink); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }
button { font: inherit; }
kbd {
  font: 500 11px/1 var(--f-mono);
  padding: 3px 5px; border-radius: 4px;
  border: 1px solid var(--rule-strong); border-bottom-width: 2px;
  color: var(--muted); background: var(--surface);
}

/* The highlighter: a hand-swiped band behind the text. */
.hl, .sidebar a.active > .nav-t, .toc a.current .toc-t {
  background-image: linear-gradient(100deg, transparent 0, var(--hl) 0.25em, var(--hl) calc(100% - 0.35em), transparent 100%);
  background-repeat: no-repeat;
  background-size: 100% 0.62em;
  background-position: 0 78%;
  -webkit-box-decoration-break: clone; box-decoration-break: clone;
}

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 30;
  display: flex; align-items: center; gap: 14px;
  height: var(--top); padding: 0 20px;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  -webkit-backdrop-filter: saturate(1.4) blur(10px); backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--rule);
}
.brand { display: flex; align-items: baseline; gap: 8px; color: var(--ink); text-decoration: none; white-space: nowrap; }
.brand:hover { color: var(--ink); }
.brand-code {
  font: 600 11.5px/1 var(--f-mono); letter-spacing: .04em;
  padding: 4px 6px 3px; border: 1.5px solid var(--ink); border-radius: 4px;
  transform: translateY(-2px);
}
.brand-name { font: 750 22px/1 var(--f-display); font-stretch: 80%; letter-spacing: -0.01em; }
.icon-btn {
  display: inline-grid; place-items: center;
  width: 38px; height: 38px; border-radius: 10px;
  border: 1px solid var(--rule); background: var(--surface); color: var(--ink-2); cursor: pointer;
}
.icon-btn:hover { border-color: var(--rule-strong); color: var(--ink); }
.menu-btn { display: none; }
.search-wrap { position: relative; flex: 1; max-width: 560px; margin-left: auto; }
.search-icon { position: absolute; left: 12px; top: 50%; transform: translateY(-50%); color: var(--muted); pointer-events: none; }
.search-kbd { position: absolute; right: 10px; top: 50%; transform: translateY(-50%); pointer-events: none; }
#search {
  width: 100%; height: 40px; padding: 0 36px 0 38px;
  border: 1px solid var(--rule); border-radius: 10px;
  background: var(--paper); color: var(--ink); font: 15px var(--f-body);
  transition: border-color .15s, background .15s, box-shadow .15s;
}
#search::placeholder { color: var(--muted); }
#search:focus { outline: none; border-color: var(--accent); background: var(--surface); box-shadow: 0 0 0 3px var(--accent-soft); }
#search:focus ~ .search-kbd { opacity: 0; }
.search-results {
  position: absolute; top: 46px; left: 0; right: 0;
  max-height: 70vh; overflow: auto; padding: 6px;
  background: var(--surface); border: 1px solid var(--rule); border-radius: var(--radius);
  box-shadow: var(--shadow);
}
.search-results a {
  display: block; padding: 10px 12px; border-radius: 8px; color: var(--ink); text-decoration: none;
}
.search-results a + a { margin-top: 2px; }
.search-results a:hover, .search-results a.active { background: var(--accent-soft); }
.sr-where { font: 500 11.5px/1.4 var(--f-mono); color: var(--muted); letter-spacing: .01em; }
.sr-title { font: 650 16px/1.35 var(--f-display); margin: 2px 0; }
.sr-snip { font-size: 13.5px; line-height: 1.5; color: var(--ink-2); }
.sr-snip mark { background: var(--hl); color: inherit; border-radius: 2px; padding: 0 1px; }
.sr-empty { padding: 12px 14px; color: var(--muted); font-size: 15px; }
.read-progress { position: absolute; left: 0; right: 0; bottom: -1px; height: 2px; pointer-events: none; }
.read-progress > div { height: 100%; background: var(--accent); transform-origin: 0 50%; transform: scaleX(0); }

/* ---------- layout ---------- */
.layout { display: flex; }
.sidebar {
  position: sticky; top: var(--top); align-self: flex-start;
  width: var(--sidebar); flex: none; height: calc(100vh - var(--top)); overflow: auto;
  padding: 20px 14px 48px; border-right: 1px solid var(--rule);
  scrollbar-width: thin;
}
.nav-group { margin-top: 22px; }
.nav-title {
  font: 600 11px/1 var(--f-mono); letter-spacing: .12em; text-transform: uppercase;
  color: var(--muted); margin: 0 10px 8px;
}
.sidebar a {
  display: flex; align-items: baseline; gap: 8px;
  padding: 6px 10px; border-radius: 8px; color: var(--ink); text-decoration: none; font-size: 15.5px; line-height: 1.35;
}
.sidebar a:hover { background: var(--accent-soft); color: var(--ink); }
.sidebar > a.active, .nav-group > a.active { font-weight: 700; }
.nav-count { margin-left: auto; font: 500 11.5px/1 var(--f-mono); color: var(--muted); }
.toc { margin: 2px 0 8px 14px; padding-left: 4px; border-left: 1.5px solid var(--rule); }
.toc a { font-size: 13.5px; padding: 4px 8px; color: var(--ink-2); gap: 10px; }
.toc a.current { color: var(--ink); font-weight: 600; }
.toc-n { flex: none; width: 1.3em; font: 500 11.5px/1.6 var(--f-mono); color: var(--muted); text-align: right; }
.toc a.toc-mod { font-weight: 600; color: var(--ink); margin-top: 6px; }
.toc a.toc-sub { font-size: 12.5px; padding: 2px 8px 2px 32px; color: var(--muted); }
.toc a.toc-sub.current { color: var(--ink); }
.toc a.in-current .toc-n { color: var(--accent); }
.main { flex: 1; min-width: 0; padding: 40px 48px 96px; }
.main:focus { outline: none; }
.doc { max-width: 780px; margin: 0 auto; }
.scrim { display: none; }

/* ---------- rendered markdown ---------- */
.doc h1, .home h1 {
  font: 780 clamp(34px, 5vw, 50px)/1.02 var(--f-display); font-stretch: 78%;
  letter-spacing: -0.02em; margin: 0 0 14px; text-wrap: balance;
}
.doc h2 {
  font: 720 28px/1.15 var(--f-display); font-stretch: 85%; letter-spacing: -0.01em;
  margin: 64px 0 14px; padding-top: 22px; border-top: 1.5px solid var(--ink);
  scroll-margin-top: calc(var(--top) + 16px); text-wrap: balance;
}
.doc h2.module-head {
  display: grid; grid-template-columns: auto minmax(0, 1fr); column-gap: 18px; row-gap: 6px; align-items: baseline;
  margin-top: 96px; padding-top: 28px; border-top: 3px solid var(--ink);
  font-size: 34px; font-stretch: 80%;
}
.doc h2.module-head .h-eyebrow { grid-column: 1 / -1; }
.doc h2.module-head .h-title { grid-column: 1 / -1; }
.doc h2.module-head .h-src {
  grid-row: 1; grid-column: 2; justify-self: end;
  font: 600 12px/1 var(--f-mono); letter-spacing: .08em; color: var(--muted);
  padding: 4px 7px; border: 1px solid var(--rule-strong); border-radius: 4px;
}
p.module-meta {
  display: flex; flex-wrap: wrap; gap: 4px 18px;
  margin: 0 0 8px; padding: 12px 16px; border-radius: 10px;
  background: var(--surface); border: 1px solid var(--rule);
  font-size: 14.5px !important; color: var(--ink-2) !important; line-height: 1.5 !important;
}
p.module-meta { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: 6px 16px; }
p.module-meta .mm { display: contents; }
p.module-meta strong { font: 600 11px/2 var(--f-mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); }
.doc h3.topic-head, .doc h2.module-head ~ h3 {
  font: 720 25px/1.2 var(--f-display); font-stretch: 85%; letter-spacing: -0.005em;
  margin: 52px 0 12px; padding-top: 16px; border-top: 1px solid var(--rule-strong);
}
.doc h3.topic-head { display: flex; flex-direction: column; gap: 4px; }
.h-eyebrow {
  font: 600 12px/1 var(--f-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--accent);
}
.h-src { font: 500 13px/1.4 var(--f-mono); color: var(--muted); letter-spacing: 0; }
.doc h3 {
  font: 680 20px/1.25 var(--f-display); font-stretch: 92%;
  margin: 36px 0 8px; scroll-margin-top: calc(var(--top) + 16px);
}
.doc h4 {
  font: 680 19px/1.3 var(--f-display); font-stretch: 94%;
  margin: 32px 0 8px; scroll-margin-top: calc(var(--top) + 16px);
}
.doc p, .doc li { overflow-wrap: anywhere; }
.doc > p:first-of-type, .page-intro { font-size: 18.5px; color: var(--ink-2); line-height: 1.6; }
.doc ul, .doc ol { padding-left: 1.3em; }
.doc li { margin: 4px 0; }
.doc li::marker { color: var(--muted); }
.doc strong { font-weight: 700; }
.doc hr { border: 0; border-top: 1px solid var(--rule); margin: 32px 0; }
.doc table {
  border-collapse: separate; border-spacing: 0; width: 100%; margin: 16px 0 22px;
  font-size: 14.5px; line-height: 1.5; display: block; overflow-x: auto;
  border: 1px solid var(--rule); border-radius: 10px; background: var(--surface);
}
.doc th, .doc td { padding: 9px 12px; text-align: left; vertical-align: top; border-bottom: 1px solid var(--rule); }
.doc tr:last-child td { border-bottom: 0; }
.doc th {
  font: 600 11.5px/1.4 var(--f-mono); letter-spacing: .06em; text-transform: uppercase;
  color: var(--muted); background: var(--paper); white-space: nowrap;
}
.doc td + td, .doc th + th { border-left: 1px solid var(--rule); }
.doc code { font: 500 0.86em var(--f-mono); background: var(--code); padding: 1px 5px; border-radius: 4px; }
.doc pre { background: var(--code); padding: 14px; border-radius: 10px; overflow-x: auto; }
.doc pre code { background: none; padding: 0; }
.doc sub, .doc sup { font-size: 0.72em; }

/* Formula + its symbol legend read as one unit. */
.math-block {
  position: relative;
  background: var(--surface); border: 1px solid var(--rule); border-radius: 10px;
  padding: 14px 18px; margin: 18px 0; overflow-x: auto;
  box-shadow: inset 3px 0 0 var(--accent);
}
.math-block .katex-display { margin: 4px 0; }
.math-block .katex { font-size: 1.12em; }
.math-block:has(+ p.where) { margin-bottom: 0; border-bottom-left-radius: 0; border-bottom-right-radius: 0; }
p.where {
  margin: 0 0 22px; padding: 10px 18px 12px;
  font-size: 14.5px; line-height: 1.6; color: var(--ink-2);
  background: var(--paper); border: 1px solid var(--rule); border-top: 1px dashed var(--rule-strong);
  border-radius: 0 0 10px 10px; box-shadow: inset 3px 0 0 var(--accent-soft);
}
.sim-callout { padding: 12px 16px; border-radius: 10px; background: var(--accent-soft); margin: 16px 0; }

/* ---------- practice questions ---------- */
.practice-bar {
  position: sticky; top: calc(var(--top) + 8px); z-index: 5;
  display: flex; flex-wrap: wrap; align-items: center; gap: 8px;
  margin: 18px 0 8px; padding: 8px 8px 8px 14px;
  background: color-mix(in srgb, var(--surface) 92%, transparent);
  -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px);
  border: 1px solid var(--rule); border-radius: 12px;
}
.practice-count { font: 500 13px var(--f-mono); color: var(--muted); margin-right: auto; }
.question {
  margin: 14px 0; padding: 16px 18px 14px;
  background: var(--surface); border: 1px solid var(--rule); border-radius: var(--radius);
}
.question > p:first-child { margin: 0; }
.question > p:first-child strong:first-child { font-family: var(--f-display); font-weight: 720; font-stretch: 90%; }
.reveal-btn {
  margin-top: 12px; padding: 6px 12px; border-radius: 8px; cursor: pointer;
  border: 1px dashed var(--rule-strong); background: transparent; color: var(--accent); font-size: 14px; font-weight: 600;
}
.reveal-btn:hover { border-style: solid; background: var(--accent-soft); }
.answer { display: none; margin-top: 12px; padding-top: 4px; border-top: 1px solid var(--rule); }
.question.open .answer { display: block; animation: rise .25s ease-out; }
.answer > :last-child { margin-bottom: 0; }

/* ---------- controls ---------- */
.chip {
  border: 1px solid var(--rule); background: var(--surface); color: var(--ink);
  border-radius: 999px; padding: 6px 14px; font-size: 14.5px; cursor: pointer; line-height: 1.3;
  transition: background .12s, border-color .12s, color .12s;
}
.chip:hover { border-color: var(--rule-strong); }
.chip.on { background: var(--ink); border-color: var(--ink); color: var(--paper); }
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  border: 1px solid var(--rule-strong); background: var(--surface); color: var(--ink);
  border-radius: 10px; padding: 9px 16px; font-size: 15px; font-weight: 600; cursor: pointer;
  text-decoration: none; line-height: 1.2;
  transition: background .12s, border-color .12s, transform .08s;
}
.btn:hover { border-color: var(--ink-2); color: var(--ink); }
.btn:active:not(:disabled) { transform: translateY(1px); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn.primary:hover { background: var(--accent-ink); border-color: var(--accent-ink); color: #fff; }
:root[data-theme="dark"] .btn.primary, :root[data-theme="dark"] .btn.primary:hover { color: #0e1524; }
.btn.ghost { border-color: transparent; background: transparent; color: var(--ink-2); font-weight: 500; }
.btn.ghost:hover { background: var(--accent-soft); color: var(--ink); }
.btn.good { border-color: var(--up); color: var(--up); background: var(--up-soft); }
.btn.bad { border-color: var(--down); color: var(--down); background: var(--down-soft); }
.btn kbd { background: transparent; border-color: currentColor; color: inherit; opacity: .7; }
.btn:disabled { opacity: .4; cursor: default; }
.check { display: inline-flex; align-items: center; gap: 8px; font-size: 14.5px; color: var(--ink-2); cursor: pointer; }
input[type="checkbox"], input[type="range"] { accent-color: var(--accent); }
select {
  font: 14px var(--f-body); color: var(--ink); background: var(--surface);
  border: 1px solid var(--rule-strong); border-radius: 8px; padding: 5px 8px;
}

/* ---------- graph paper (where curves live) ---------- */
.graph-paper {
  background-color: var(--surface);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 20px 20px;
  background-position: -1px -1px;
}

/* ---------- home ---------- */
.home { max-width: 1080px; margin: 0 auto; }
.hero { display: grid; gap: 28px; }
.eyebrow { font: 600 12px/1 var(--f-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); margin: 0 0 16px; }
.home h1 { font-size: clamp(44px, 7.4vw, 88px); line-height: .92; letter-spacing: -0.03em; margin-bottom: 18px; }
.home h1 .hl { background-size: 100% 0.42em; background-position: 0 86%; padding: 0 .04em; }
.lede { font-size: 19px; line-height: 1.55; color: var(--ink-2); max-width: 36ch; margin: 0; }
.drill {
  display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr);
  background: var(--surface); border: 1px solid var(--rule); border-radius: 16px; overflow: hidden;
  box-shadow: var(--shadow);
}
.drill-graph { border-right: 1px solid var(--rule); min-height: 300px; display: grid; place-items: center; padding: 8px; }
.drill-graph svg { width: 100%; height: auto; display: block; overflow: visible; }
.g-axis { fill: none; stroke: var(--ink); stroke-width: 1.6; }
.g-axlab { font: 600 16px var(--f-mono); fill: var(--ink); }
.g-tick { font: 600 15px var(--f-mono); fill: var(--muted); }
.g-tick-new { fill: var(--accent); font-weight: 600; }
.g-guide { fill: none; stroke: var(--muted); stroke-width: 1; stroke-dasharray: 3 4; opacity: .7; }
.g-guide-new { stroke: var(--accent); opacity: 1; }
.g-curve { stroke: var(--ink-2); stroke-width: 2.6; stroke-linecap: round; }
.g-new { stroke: var(--accent); stroke-width: 3.2; stroke-linecap: round; opacity: 0; }
.g-lab { font: 700 15px var(--f-mono); fill: var(--ink-2); }
.g-lab-new { fill: var(--accent); opacity: 0; }
.g-note { font: 600 13px var(--f-mono); fill: var(--accent); }
.g-mover { transform: translateX(0); transition: transform .9s cubic-bezier(.6, 0, .2, 1); }
.g-after { opacity: 0; transition: opacity .35s ease .75s; }
.g-dot { fill: var(--ink); stroke: var(--surface); stroke-width: 2.5; transition: transform .9s cubic-bezier(.6, 0, .2, 1), fill .3s; }
.shifted .g-mover { transform: translateX(var(--dx)); }
.shifted .g-new, .shifted .g-lab-new { opacity: 1; transition: opacity .2s; }
.shifted .g-after { opacity: 1; }
.shifted .g-dot { fill: var(--accent); }

.drill-panel { padding: 22px 24px 24px; display: flex; flex-direction: column; }
.drill-head { display: flex; justify-content: space-between; align-items: baseline; }
.drill-label, .drill-streak { font: 600 11px/1 var(--f-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); }
.drill-streak { color: var(--up); }
.drill-shock { font: 760 44px/1.05 var(--f-display); font-stretch: 85%; margin: 14px 0 4px; letter-spacing: -0.01em; }
.drill-shock sub, .drill-shock sup { font-size: .5em; }
.drill-name { color: var(--ink-2); font-size: 16px; }
.drill-choices { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; margin: 20px 0 0; }
.drill-choice {
  padding: 12px 8px; border-radius: 10px; cursor: pointer;
  border: 1.5px solid var(--rule-strong); background: var(--paper); color: var(--ink);
  font: 700 15px var(--f-body); transition: border-color .12s, background .12s, transform .08s;
}
.drill-choice:hover:not(:disabled) { border-color: var(--ink); background: var(--surface); }
.drill-choice:active:not(:disabled) { transform: translateY(1px); }
.drill-choice:disabled { cursor: default; opacity: .55; }
.drill-choice.is-right { opacity: 1; border-color: var(--ink); background: var(--hl-strong); color: #14213d; }
.drill-choice.is-wrong { opacity: 1; border-color: var(--down); color: var(--down); text-decoration: line-through; text-decoration-thickness: 2px; }
.drill-result { margin-top: 16px; font-size: 15px; line-height: 1.55; animation: rise .3s ease-out; }
.drill-result p { margin: 0 0 12px; color: var(--ink-2); }
.drill-verdict { font-weight: 700; }
.drill-verdict.ok { color: var(--up); }
.drill-verdict.miss { color: var(--down); }
.drill-signs { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 16px; }
.drill-actions { display: flex; flex-wrap: wrap; gap: 8px; }

.sign {
  display: inline-flex; align-items: baseline; gap: 5px;
  padding: 3px 8px; border-radius: 6px; font: 700 14px/1.3 var(--f-mono);
  background: var(--paper); border: 1px solid var(--rule); color: var(--muted);
}
.sign-var { font-weight: 500; color: var(--ink-2); }
.sign.up { color: var(--up); background: var(--up-soft); border-color: transparent; }
.sign.down { color: var(--down); background: var(--down-soft); border-color: transparent; }
.sign.q { color: var(--warn); }

.home-section { margin-top: 56px; }
.section-label {
  display: flex; align-items: center; gap: 14px;
  font: 600 12px/1 var(--f-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); margin: 0 0 16px;
}
.section-label::after { content: ""; flex: 1; border-top: 1px solid var(--rule-strong); }
.section-note { color: var(--ink-2); margin: -4px 0 16px; font-size: 15.5px; }
.tiles { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; }
.tiles-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.tile {
  display: flex; flex-direction: column; gap: 6px; min-height: 112px;
  padding: 16px 18px; border-radius: var(--radius); text-decoration: none; color: var(--ink);
  background: var(--surface); border: 1px solid var(--rule);
  transition: border-color .15s, transform .15s, box-shadow .15s;
}
.tile:hover { color: var(--ink); border-color: var(--ink-2); transform: translateY(-2px); box-shadow: var(--shadow); }
.tile-title { font: 720 21px/1.1 var(--f-display); font-stretch: 85%; }
.tile-meta { font-size: 14px; color: var(--muted); }
.meter { margin-top: auto; height: 6px; border-radius: 99px; background: var(--rule); overflow: hidden; }
.meter > span { display: block; height: 100%; background: var(--up); border-radius: 99px; }

.path { list-style: none; margin: 0; padding: 0; border-top: 1px solid var(--rule); }
.path li { border-bottom: 1px solid var(--rule); }
.path a {
  display: grid; grid-template-columns: 3rem minmax(0, 1fr) auto; align-items: baseline; column-gap: 12px; row-gap: 4px;
  padding: 14px 6px; color: var(--ink); text-decoration: none;
}
.path a:hover { background: var(--accent-soft); color: var(--ink); }
.path-n { font: 700 28px/1 var(--f-display); font-stretch: 75%; color: var(--accent); }
.path-title { font: 650 19px/1.25 var(--f-display); font-stretch: 92%; }
.path-src { font: 600 11.5px var(--f-mono); color: var(--muted); text-align: right; letter-spacing: .06em; }
.path-topics { grid-column: 2 / -1; font-size: 14.5px; color: var(--ink-2); line-height: 1.45; }

/* ---------- flashcards ---------- */
.fc-controls { display: flex; flex-wrap: wrap; gap: 12px 18px; align-items: center; margin: 20px 0 18px; }
.segmented { display: inline-flex; flex-wrap: wrap; gap: 6px; }
.fc-stats { display: flex; gap: 18px; color: var(--muted); font: 500 13px var(--f-mono); margin: 0 0 8px; flex-wrap: wrap; }
.fc-stats b { color: var(--ink); font-weight: 600; }
.st-known b { color: var(--up); }
.st-learning b { color: var(--down); }
.st-left { margin-left: auto; }
.progress { height: 5px; background: var(--rule); border-radius: 999px; overflow: hidden; margin-bottom: 22px; }
.progress > div { height: 100%; background: var(--up); transition: width .3s ease; }
/* An index card: blue ruled lines, red header rule. */
.card {
  position: relative; min-height: 300px; border-radius: 6px; cursor: pointer;
  background-color: var(--surface);
  background-image: repeating-linear-gradient(to bottom, transparent 0 31px, var(--card-rule) 31px 32px);
  background-position: 0 58px;
  border: 1px solid var(--rule); box-shadow: var(--shadow);
  display: flex; flex-direction: column;
  transition: transform .15s ease;
}
.card:hover { transform: translateY(-1px); }
.card-head {
  display: flex; justify-content: space-between; align-items: center;
  height: 58px; padding: 0 26px; border-bottom: 2px solid var(--card-margin);
  background: var(--surface); border-radius: 6px 6px 0 0;
}
.deck-tag { font: 600 11.5px/1 var(--f-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); }
.card-status { font: 600 11px/1 var(--f-mono); padding: 4px 7px; border-radius: 99px; letter-spacing: .04em; }
.card-status.known { color: var(--up); background: var(--up-soft); }
.card-status.learning { color: var(--down); background: var(--down-soft); }
.card-body { padding: 26px 26px 30px; flex: 1; display: flex; flex-direction: column; justify-content: center; }
.card .front { font: 700 clamp(22px, 3vw, 28px)/1.25 var(--f-display); font-stretch: 90%; text-wrap: balance; }
.card.flipped .card-body { justify-content: flex-start; }
.card .back {
  margin-top: 18px; padding: 16px 18px; font-size: 16.5px; line-height: 1.6;
  background: var(--paper); border-radius: 8px; border-left: 3px solid var(--accent);
  animation: rise .22s ease-out;
}
.card .back > :first-child { margin-top: 0; }
.card .back > :last-child { margin-bottom: 0; }
.card .back table { font-size: 13.5px; }
.card-hint { position: absolute; bottom: 12px; right: 18px; font: 500 12px var(--f-mono); color: var(--muted); }
.card.done { cursor: default; }
.card.done p { color: var(--ink-2); }
.fc-actions { display: flex; gap: 10px; justify-content: center; margin: 22px 0 0; flex-wrap: wrap; }
.fc-secondary { margin-top: 10px; }

/* ---------- simulator ---------- */
.sim-top {
  display: grid; gap: 14px; margin: 20px 0 16px; padding: 16px;
  background: var(--surface); border: 1px solid var(--rule); border-radius: var(--radius);
}
.shock-row { display: flex; flex-wrap: wrap; gap: 6px; }
.shock-row .chip { font-family: var(--f-mono); font-size: 14px; }
.sim-options { display: flex; flex-wrap: wrap; gap: 12px 22px; align-items: center; font-size: 14px; color: var(--ink-2); padding-top: 12px; border-top: 1px solid var(--rule); }
.sim-options label { display: flex; align-items: center; gap: 8px; }
.sim-options .size input { width: 140px; }
.legend { display: flex; gap: 18px; font: 500 12.5px var(--f-mono); color: var(--muted); margin: 0 0 10px; }
.swatch { display: inline-block; width: 22px; height: 3px; vertical-align: middle; margin-right: 8px; border-radius: 2px; }
.panels { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; }
.panel { border: 1px solid var(--rule); border-radius: var(--radius); padding: 12px 10px 6px; }
.panel h4 { margin: 0 8px; font: 700 17px/1.2 var(--f-display); font-stretch: 90%; }
.panel svg { width: 100%; height: auto; display: block; }
.panel svg text { font-family: var(--f-mono); }
.panel .sub { margin: 2px 8px 6px; font-size: 13px; color: var(--muted); line-height: 1.4; }
.sim-table { margin: 20px 0; overflow-x: auto; }
.sim-table table {
  border-collapse: separate; border-spacing: 0; width: 100%; font: 500 14.5px var(--f-mono);
  background: var(--surface); border: 1px solid var(--rule); border-radius: var(--radius); overflow: hidden;
}
.sim-table th, .sim-table td { padding: 9px 8px; text-align: center; border-bottom: 1px solid var(--rule); }
.sim-table tr:last-child td, .sim-table tr:last-child th { border-bottom: 0; }
.sim-table thead th { background: var(--paper); color: var(--ink); font-weight: 600; }
.sim-table tbody th { text-align: left; padding-left: 14px; color: var(--muted); font-weight: 500; font-size: 12.5px; letter-spacing: .06em; text-transform: uppercase; }
.sim-table tbody tr:first-child { background: var(--accent-soft); }
.sign-up { color: var(--up); font-weight: 700; font-size: 17px; }
.sign-down { color: var(--down); font-weight: 700; font-size: 17px; }
.sign-zero { color: var(--muted); }
.sign-q { color: var(--warn); font-weight: 700; }
.steps { background: var(--surface); border: 1px solid var(--rule); border-radius: var(--radius); padding: 18px 22px; }
.steps-head { display: flex; flex-wrap: wrap; align-items: baseline; gap: 6px 12px; }
.steps-head strong { font: 720 20px/1.2 var(--f-display); font-stretch: 88%; }
.steps-type, .steps-curve { font: 600 11px/1 var(--f-mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); }
.steps-curve { color: var(--accent); margin-left: auto; }
.steps ol { margin: 12px 0 0; padding-left: 22px; }
.steps li { margin: 6px 0; }
.steps li::marker { font: 600 13px var(--f-mono); color: var(--muted); }

@keyframes rise { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: none; } }

/* ---------- wide: hero copy beside the drill ---------- */
@media (min-width: 1180px) {
  .hero { grid-template-columns: minmax(0, 0.8fr) minmax(0, 2fr); align-items: center; gap: 40px; }
  .drill { grid-template-columns: minmax(0, 1.15fr) minmax(0, 1fr); }
}

/* ---------- small screens ---------- */
@media (max-width: 1000px) {
  .tiles { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 900px) {
  .menu-btn { display: inline-grid; }
  .topbar { padding: 0 12px; gap: 10px; }
  .sidebar {
    position: fixed; left: 0; top: var(--top); z-index: 25;
    background: var(--paper); box-shadow: var(--shadow);
    transform: translateX(-100%); transition: transform .22s ease; visibility: hidden;
  }
  .sidebar.open { transform: none; visibility: visible; }
  .scrim:not([hidden]) { display: block; position: fixed; inset: var(--top) 0 0 0; z-index: 20; background: rgba(14, 21, 36, .35); }
  .main { padding: 24px 16px 72px; }
  .panels { grid-template-columns: 1fr; }
  .drill { grid-template-columns: 1fr; }
  .drill-graph { border-right: 0; border-bottom: 1px solid var(--rule); min-height: 0; }
  .brand-name { display: none; }
  .search-kbd { display: none; }
  .doc h2 { margin-top: 48px; font-size: 25px; }
  .doc h2.module-head { margin-top: 72px; font-size: 29px; }
  .doc h3.topic-head, .doc h2.module-head ~ h3 { font-size: 22px; }
}
@media (max-width: 560px) {
  body { font-size: 16.5px; }
  .tiles, .tiles-2 { grid-template-columns: 1fr; }
  .tile { min-height: 0; }
  .drill-panel { padding: 18px; }
  .drill-shock { font-size: 36px; }
  .path a { grid-template-columns: 2.2rem minmax(0, 1fr); }
  .path-src { grid-row: 1; grid-column: 2; text-align: left; }
  .path-title { grid-column: 2; }
  .st-left { margin-left: 0; }
  .card-head, .card-body { padding-left: 18px; padding-right: 18px; }
  .card-hint { display: none; }
  .steps-curve { margin-left: 0; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
}